Flame retardant compositions

ABSTRACT

CROSSLINKABLE ETHYLENE-VINYL ACETATE COPOLYMER COMPOSITIONS CONTAINING SILANE-TREATED HYDRATED INORGANIC FILLERS ILLUSTRATING IMPROVED MOISTURE, HEAT RESISTANCE AND FLAME RETARDANCE. AN ELECTRICAL CONDUCTOR COATED WITH SUCH A COPOLYMER COMPOSITION IS A PARTICULARLY IMPORTANT APPLICATION.

United States Patent 3,832,326 FLAME RETARDANT COMPOSITIONS Joyce A.North, Somerset, N.J., and Gerard W. Kuckro, Cincinnati, Ohio, assignorsto National Distillers and Chemical Corporation, New York, N.Y.

No Drawing. Continuation-impart of abandoned application Ser. No.153,120, June 14, 1972. This application June 1, 1972, Ser. No. 258,679

Int. Cl. C08f 45/04 US. Cl. 260-4229 5 Claims ABSTRACT OF THE DISCLOSURECrosslinkable ethylene-vinyl acetate copolymer compositions containingsilane-treated hydrated inorganic fillers illustrating improvedmoisture, heat resistance and flame retardance. An electrical conductorcoated with such a copolymer composition is a particularly importantapplication.

BACKGROUND OF THE INVENTION This application is a continuation-in-partof Ser. No. 153,120 filed June 14, 1971, now abandoned.

Field of the Invention The invention relates to crosslinkable polymericcompositions illustrating, inter alia, improved moisture, heatresistance and flame retardance particularly adapted for coatingelectrical wires and cable as well as for molding products requiringflame retardancy.

Description of the Prior Art One of the most important areas where fireresistant polymer compositions find use is in the electricalenvironment, i.e., where both insulating and fire resistant propertiesare sought, most especially in the area of conductor insulation.Extrudable compositions presently available to the wire and cable artare required, for flame resistance, to contain halogenated polymers suchas chlorinated polyethylene, polyvinyl chloride, chlorobutadiene,chlorinated paraffin, etc., together with antimony trioxide, bothcomponents being present in sizable quantities. Alternatively, a coatingof chlorosulfonated polyethylene paint must be applied to a non-flameretardant insulating compound which constitutes an additionalmanufacturing operation.

For certain types of dry transformers, particularly high voltagetransformers, a problem existed in that electrical failures occurred dueto surface creepage of the organic insulating component used. Theproblem was solved through the addition of hydrated alumina tocompositions whose organic binder consisted of butyl rubber, epoxyresins or polyester resins. However, these compositions do not possess abalance of excellent extrudability characteristics, physical andelectrical properties, heat resistance and flame retardance. Suchcompositions are disclosed in US. Pats. 2,997,526-7 and 8, Kessel et al.The described compositions for such usage have poor tensile strength,elongation and percent elongation retained after ageing.

The art has further proposed that various layers of graded insulatedcable be formed of crosslinked polyethylene and copolymers thereof, asilane and titanium dioxide. For instance, in US. Pat. 3,433,891 Zysk etal. it is taught that by altering the proportion of titanium dioxide invarious layers of a graded insulation the specific inductive capacitanceof the insulation can be varied. Such graded insulations are intendedfor high kv. use, e.g., 69 kv., where water of hydration is unacceptableand where high vinyl acetate copolymers such as ethylene-vinyl acetatecopolymers are contraindicated due to their harmful effect on high kv.electrical properties at proportions much over 2 to 3%. The individuallayers in a graded insulation such as Zysk et al. cannot be consideredindividually but must 3,832,326 Patented Aug. 27, 1974 SUMMARY OFINVENTION A First retarding polymeric compositions exhibiting, interalia, improved moisture and heat resistance consist essentially of anintimate mixture of at least one crosslinkable polymer containing as amajor component an ethylenevinyl acetate copolymer, one or more silanesand one or more hydrated inorganic fillers.

Such compositions have a unique combination, or balance, of improvedphysical and electrical properties to gether with a high degree of flameand fire retardance. These highly desirable results are achieved withoutthe use of halogenated polymers such as polyvinyl chloride andchlorosulfonated polyethylene, thereby eliminating hydrogen chloridefumes; without carbon black, thereby permitting its use as coloredinsulations; without any flame retardant coatings such as are currentlyrequired, thereby eliminating an additional step in manufacturingoperations when the compositions are used as, e.g., insulating compoundsextruded onto a conductor; and without antimony trioxide, therebyeliminating a very expensive compound.

Such compositions find particular use as white (an inherent property)and colored uniinsulation compositions, which can be extruded overmetal, e.g., copper or aluminum, conductors, to provide a single layerinsulating and jacketing composition which is rated according to U.L.standards for C. operation, and in some cases operation at temperaturesas high as at up to 600 volts.

Insulating compositions of the present invention find particular utilityin the insulation of building wire, appliance wire, and automotive wirewhere a unique combination of superior electrical properties combinedwith resistance to the degradative effects of heat and flame areessential, and where low smoke density and non-corrosive fumes aredesirable.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION Thenovel compositions of the present invention consist essentially of threecomponents:

(1) one or more crosslinkable or curable ethylene-vinyl acetatecopolymers;

(2) one or more silanes; and

(3) one or more hydrated inorganic fillers.

The Crosslinkable Ethylene-Vinyl Acetate Copolymer Component The termscrosslinkable or crosslinking are ascribed their normal art recognizedmeaning in the present application, i.e., they denote the formation ofprimary va-- lence bonds between polymer molecules.

Crosslinking can be accomplished by any of the known procedures such aschemical means including peroxide crosslinking; by radiation usingcobalt-60, accelerators, fi-rays, rays, electrons, X-rays, etc.; or bythermal crosslinking. The basic procedures for crosslinking polymers areextremely well known to the art and need not be described here indetail.

The polymeric component of the present composition is based upon anethylene-vinyl acetate copolymer. The most preferred polymericconstituent is an ethylene-vinyl acetate copolymer per se containing atleast about 9% vinyl acetate, balance ethylene. Amounts of vinyl acetateup to about 40% or higher can be used, but at amounts greater than about28% vinyl acetate, tensile strength and ultimate elongation suffer.

Although little is gained, and some properties are even harmed, it ispossible to include minor proportions of other crosslinkable polymers orcopolymers in the composition of this invention. However, ethylenevinylacetate copolymers, as described above, should comprise at least about66% of the total polymers present. Representative of such minorpolymeric components which can be used in such non-preferred embodimentsinclude polyethylene, copolymers of ethylene with propylene, butene, theacrylates and maleates, polydimethyl siloxane andpolymethylphenylsiloxane, copolymers of vinyl acetate with theacrylates, etc. Obviously, mixtures of these minor polymeric componentscan be used.

. Terpolymers of ethylene and vinyl acetate derived from, e.g., any ofthe corresponding monomeric materials listed above (other than ethyleneor vinyl acetate) can be used. A representative terpolymer would be anethylene-vinyl acetate-maleate.

. The ethylene-vinyl acetate copolymers used in our invention preferablyhave a melt index of from about 1.0 to about 20.0.

The polyethylenes useful in the present invention include essentiallyall high, medium and low density polyethylenes as well as mixturesthereof. The most preferred polyethylenes for blending for use asuniinsulation for electrical wires and cables generally have a densityof from about 0.900 to about 0.950 gm./cc. and a melt index of fromabout 1.0 to about 10.0.

Few reasons exist for using anything other than an ethylene-vinylacetate copolymer per se, since this material is readily available atlow cost. Moreover for some reason unknown at this time, theethylene-vinyl acetate copolymer provides results superior to otherpolymers when'combined with the silane and the hydrated inorganicfiller.

More specifically, the compositions of the present invention provide asuperior and unexpected balance of:

(1) low temperature brittleness, i.e., the composition will not readilycrack during low temperature movement (ASTM D 746.)

(2) heat resistance after ageing, i.e., excellent elongation afterextended service at 90 C. and even 125 C.

(3) arcing and tracking resistance, as high at kv., whereas evenporcelain shows surface breakdown at 4 kv. This property is not oftenrequired, however, in the preferred environment of under 600 voltservice.

(4) flame resistance and flame retardance.

(5) moisture resistance, i.e., low mechanical absorption of water whichyields a superior dielectric constant.

(6) resistance to industrial chemicals.

It is not known why the compositions of this invention provide such asuperior balance of properties. It is possible to theorize that there issome synergistic relationship between the ethylene-vinyl acetatecopolymer, silane and hydrated inorganic filler, but there is nointention to be bound by such a theory. However, it has been establishedthat for low voltage environments, less than 5000 volts, even moreparticularly for less than 600 volt environments, the compositions ofthis invention are superior to any known to the prior art for service asuniinsulation. Uniinsulation is an art accepted term denoting insulationwhere one layer is extruded around the conductor, and this one layerserves as the electrical insulation and the jacketing to providephysical and flame protection. The present compositions are especiallyadapted for service as uniinsulation in the under 5000 volt, mostespecially in theunder 600 volt range, where only a single extrudedcoatin is used, and it is in the environment that a superior balance ofproperties is required. It has been further found that ethylene-vinylacetate copolymers will hold very large amounts of filler and stillprovide high flexibility and a high degree of crosslinking. Thesimultaneous achievement of high filler loading, flexibility andcrosslinking is quite surprising as high flexibility and highcrosslinking are generally believed incompatible, as are highcrosslinking and high filler loading (which implies low cross linkablepolymer content). Ethylene-vinyl acetate copolymers further providesuperior fire retardance to the polymeric compositions of the presentinvention.

The above described ethylene-vinyl acetate copolymers are preferablycrosslinked by irradiation with high-energy electron beams or throughthe use of chemical crosslinking additives. Fully crosslinked, thesepolymers become thermoset in behavior.

Chemical crosslinking is accomplished by incorporating a crosslinkingagent, e.g., dicumyl peroxide, into the ethylene-vinyl acetatecopolymer. The peroxide is later activated during processing to link theethylene-vinyl acetate polymer chains into a three-dimensional network(and other minor amounts of crosslinkable polymer, if present).

The chemical crosslinking is carried out in accordance with procedureswell known to the art, and variations in the general crosslinkingconditions set out below will be apparent to one skilled in the art. Thepresent invention is moreover, not limited to the use of tertiaryorganic peroxides for chemical crosslinking, and other art recognizedmaterials which decompose to provide free radicals can be used.Obviously such crosslinking agents should not decompose duringcompounding of the composition, but the selection of acceptablecrosslinking agents will be apparent to those skilled in the art.

Generally speaking, as the amount of crosslinking agent used increases,the degree of polymer crosslinking increases. Usually no more than 10%(based on polymer) of the organic tertiary peroxides need be used, with3 to 6% being more typical values. Other crosslinking agents may requiredifferent amounts, but these can be readily determined. It is oftenadvisable to avoid very low amounts of crosslinking agents, since someloss of resistance to deformation under sudden or continuous pressuremay ensue. Crosslinking coagents such as triallylcyanurate and the likemay also be included to increase the effectiveness of the crosslinkingagent.

The tertiary organic peroxides, as with most other chemical crosslinkingagents, are activated by heating to above their activation temperaturewhereupon decomposition thereof occurs. Any of the known procedures canbe used to accomplish activation, e.g., high pressure steam applicationto the composition.

The art of radiation crosslinking is so highly developed that littleneed be said with respect to such procedures. As higher total doses ofradiation are used, the degree of crosslinking generally increases, andfor preferred crosslinkings a total radiation dose above 20 megaradswill be used. Lower values are acceptable, but generally lower theamount of crosslinking. However, the dose should not be so high as tocause polymer degradation.

Crosslinking is generally conducted at superatmospheric pressures, e.g.,on the order of 200 to 400 p.s.i., although higher or lower pressuresmay be used. Pressure is employed to avoid uncontrolled porosity in thepolymer, which would be highly undesirable in electrical insulation.

In general, the higher the degree of crosslinking the more resistant thepolymeric composition is to moisture, chemical reagents, etc., and theless resistant the polymeric composition is to abrasion. At lowerdegrees of crosslinking there is also some loss of heat resistance aswell as a pronounced elfect on percent elongation after ageing. Theexact degree of crosslinking can, of course, be varied to. take theabove factors and their effect on the final product into account.Although higher or lower values can be used, for wire and cableinsulation a crosslinking percentage on the order of about forethylene-vinyl acetate is generally preferred, determined by extractionweight of soluable components in the crosslinked polymer.

One or more substituted silanes comprise the second essential componentof the polymeric compositions of the present invention.

Any silane may be used in the present invention which will not adverselyaffect the desired balance of properties and which will help to bind thepolymer and inorganic filler of the present invention, provided that thesilane is not combustible, e.g., alkoxy and amine silanes, and does notinterfere with polymer crosslinking or degrade during polymerprocessing.

The reasons why the silane component has such an unexpectedly favorableinfluence on the balance of properties of the present compositions areunknown. One might expect the silane to act merely as a mixingassistant, but if the silane is omitted, an inexplicable lowering ofproperties such as tensile strength and percent retention of elongationafter ageing (a 4 to 5 fold decrease) results. There is no knowntheoretical basis for the surprising effect of silanes on the thermalproperties of these polymeric compositions.

The preferred silanes used in forming the insulating compositions arethe alkoxy silanes, e.g., lower alkyl-, alkenyl-, and alkynyl-alkoxysilanes. Specific examples of such silanes are methyltriethoxy-,methyltris (2 methoxyethoxy)-, dimethyldiethoxy-, alkytrimethoxy-,vinyltris (2- methoxyethoxy)-, vinyltrimethoxyand vinyltriethoxysilane.

It is preferred to use the vinyl silanes for best results, and of thevinyl silanes the following are especially preferred:

gamma-Methacryloxypropyltrimethoxy-Silane and Vinyl-Tris(Beta-Methoxyethoxy) Silane H C :CHSi (OCH CH OCH 3 The HydratedInorganic Filler Component The fillers used in the present invention arethe hydrated inorganic fillers, e.g., hydrated aluminum oxides (A1 0 3HO or Al(OH) hydrated magnesia, hydrated calcium silicate. Of thesecompounds, the most preferred is hydrated aluminum oxide.

To obtain the superior balance of properties described, it is mandatorythat a hydrated inorganic filler be used in formulating the polymericcompositions. It must be emphasized that large proportions of anothertype of filler, be it inert or not, cannot be added to the compositionsand still achieve the superior balance of properties. For instance,replacing the hydrated inorganic filler with a comparable amount oftitanium dioxide might increase flame resistance (merely by lowering theproportion of polymer present) but would adversely affect tensilestrength and low temperature properties. Thus, the superior balance ofproperties has been lost. On the other hand, if one were to use thehydrated inorganic filler of this invention plus an equal amount ofanother filler, e.g., titanium dioxide, the superior balance of physicalproperties of our composition would suffer, e.g., percent retainedelongation after heat ageing and tensile strength.

The water of hydration in the inorganic filler must be released duringthe application of heat sufficient to cause combustion or ignition ofthe ethylene-vinyl acetate copolymer. The water of hydration chemicallybound to the inorganic filler is released endothermically. It has beenfound that the hydrated inorganic filler increased flame retardance in amanner far superior to other fillers previously used by the art toprovide insulation with flame retardance, e.g., carbon black, clays,titanium dioxide, etc.

i What is even more surprising is that flame retardance is combined withexcellent electrical insulation properties at the high filler loadingsused, since at these loadings the copolymeric composition contains alarge amount of bound water.

The filler size is relatively non-important and may be in accordancewith those sizes used by the prior art.

The Proportions of the Components The amounts of the polymer and fillercan be varied within wide proportions. However, the silane percentageshould be in the range of from about 0.5 to 5.0 parts per 100 parts ofthe filler. Lower amounts may be insufficient to provide adequatesurface treatment while larger quantities could have an adverse effecton some of the physical properties, i.e., elongation, of an extrudedinsulating compound after crosslinking.

Best results are obtained in coating, e.g., extruding, onto electricalwires and cables when from to 400 or more weight parts of filler (mostpreferable at least 125-150 weight parts), 0.5 to 5.0 weight parts ofsilane and weight parts of polymer are present.

The compositions of the present invention may be formed in a number ofways. However, in every instance it is necessary that the filler andsilane be intimately contacted. For instance, the preferred method offiller treatment is by direct addition of the silane to the polymerfollowed by addition thereto of the filler and other adiitives, ifdesired. This can be done in an internal mixer, such as a Banbury orWerner & Pfieiderer mixer. Alternatively, the silane may be addeddirectly to the filler, dispersed therein, and the polymer then added.

Any processing device known to the art which insures an intimate mixtureof all three essential components may be used, provided the silane isintimately and thoroughly dispersed onto the surface of the hydratedinorganic filler.

It will be apparent that in addition to the three essential componentsof the compositions of this invention, other additives may be present,e.g., pigments, stabilizers, antioxidants (e.g., polymerizedtrimethyldihydro quinoline) so long as they do not interfere withcrosslinking, when desired, or harm desired properties. Such materialsare present in very minor proportions, ranging from less than 10% of thepolymer, and usually in amounts of less than 5%. There are two reasonsamounts of other components are not desirable: firstly, the presentcomposition per se has such superior properties; secondly, anysignificant amounts of other fillers for example, serve only to degradeor upset the balance of properties.

For the formation of insulation on conductors by extrusion, the mostpreferred embodiment of this invention, a fourth component is generallynecessary, i.e., a lubricant such as a fatty acid soap or metallicderivative thereof. Such a material is also important to improve thestripping properties of wire insulation and thereby to permit theinsulation to be easily stripped from the wire by the user to facilitatesplicing and to make terminations. It is necessary to avoid, however,soaps which interfere with the crosslinking reaction (free radicalmechanism) such as zinc stearate, which will react with organicperoxides. Acceptable soaps are the alkaline earth metal fatty acidsoaps. A preferred soap is calcium stearate. Additional representativeexamples of useful lubricants include the alkaline earth metal salts andaluminum salts of stearic acid, oleic acid, palmitic acid and otherfatty acids used by the art for this purpose, silicone oil, etc.

The following examples are provided to further illustrate certainaspects of this inveintion. In each instance the recited silane andfiller (Al O -3H O) were separately blended to intimately coat thesilane onto the surface of.

the filler. Thereafter the silane/filler and the other additionalcomponents were added to the polymer and blended therewith. Care wastaken to control the temperature rise during the mixing so as to notactivate the peroxide prior to the completion of blending. Followingmixing, the polymer composition was extruded onto a copper wire using aBrabender extruder and raised to the peroxide activation temperature byvulcanization in steam under high pres sure.

COMPOSITION 1 'Ethylene-Vinyl Acetate a 100.0

Vinyl-Tris (fl-Methoxyethoxy) Silane 3.0 Polymerized TrimethyldihydroQuinoline 2.0 Al O -3H O Calcium Stearate 2.0 65% 1,2 and 35,% 1,3-Bis(Tert. Butyl-Peroxyisopropyl) Benzene 1.4

208.4 a 17% Vinyl Acetate; 1.5 Melt Index.

COMPOSITION 2 Ethylene-Vinyl Acetate 100.0 Vinyl-Tris (B-Methoxyethoxy)Silane 3.0 Polymerized Trimethyldihydro Quinoline 0.5 Al O -3H O 125.0Calcium Stearate 2.0 65% 1,2 and 35% 1,3-Bis (Tert.Butyl-Peroxyisopropyl) Benzene 1.7

232.2 17% Vinyl Acetate 1.0 Melt Index.

COMPOSITION 3 Ethylene-Vinyl Acetate 100.0 Polymerized TrimethyldihydroQuinoline 0.5 Al O -3H O (Silane treated) 150.0 Calcium Stearate 2.01,4-Bis (Tert. Butyl Peroxy-isopropyl) Benzene 1.7

254.2 28% Vinyl Acetate; 3.0 Melt Index. Vinyl-Tris (fl-Methoxy) Silane.

COMPARATIVE EXAMPLE (NO SILANE ADDITION) Ethylene-Vinyl Acetate a 100.0Polymerized Trimethyldihydro Quinoline 1.0 A12O33H2O Titanium Dioxide5.0 Calcium Stearate 2.0 2,5-Dimethyl-2, S-di (t-Butylperoxy) Hexyne-36.0

194.0 17% Vinyl Acetate; 1.5 Melt Index. Added as a colorant.

Flammability tests were then performed on the described compositions andseveral prior art resins. These are described below:

Limiting Oxygen Index Test A Limiting Oxygen Index Tester (Model JD-14)was used to measure flammability in accord with ASTM D- 2863. The oxygenindex is defined as the minimum volume of oxygen in a slowly risingoxygen-nitrogen atmosphere that will sustain steady candle-like burningof a stick of polymeric material. The sample, in stick form, issupported vertically within the confines of a glass cylinder or chimney.An oxygen-nitrogen mixture filtered through glass beads enters thebottom of the cylinder and is allowed to flow upward through the tube.Glass tubing with a small gas flame at the orifice is inserted downthrough the chimney to ignite the top of the sample. Upon ignition, theflow of oxygen-nitrogen is carefully regulated to maintain a candle-likeflame. The gas flow is controlled to determine the limit offlammability, which is the difference betwen complete burning of thesample or extinction. Since the flame burns downward from the top of thesample, heating by convection is practically eliminated. In this way theheated vapors rising during combustion cannot preheat the samples, andby varying the oxygen content it is possible to determine within onepercent the minimum oxygen content to support combustion. In theLimiting Oxygen Index test, it is customary for samples to be preparedfrom slab stock, in the case of thermoplastics a simple moded plaque ora cured plaque for the vulcanizable materials. However, for use incables such materials must obviously be extruded over a conductor,usually copper or aluminum. It was thus necessary to introduce a newdimension to the LOI test in order to properly evaluate the burningbehavior of a sample when it comprised a segment of insulated conductorwith the conductor in place formed as heretofore indicated. 32 mil thickinsulation on 14 gauge wire was used. The procedure followed Wasdescribed in the March 1970 issue of Modern Plastics at page 124.

DETERMINATIONS OF LIMITING OXYGEN INDICES OF VARIOUS MATERIALS SlabMaterial: Oxygen Index Coated Wire Material:

Polyvinyl chloride, Geon 101 (without plasticizer) 45.0 Composition 131.5 Composition 2 37.0 Composition 3 51.0 Composition 4 (Comparative) 28.0

Horizontal and Vertical Flame Test Two other types of flammability testincluded the horizontal and vertical flame tests in accordance with theUnderwriters Laboratories Method 83. Essentially, the horizontal testmeasures the ability of an insulation to minimize or limit the spread offlame and materials passing this test are considered slow-burning. Themore severe vertical test measures the ability of an insulation to beself-extinguishing. In both cases, the flame temperature is on the orderof 2,300 P.

Modified General Electric Dip Track Test The Modified General ElectricDip-Track test, which strictly speaking, is not a flammability test,nonetheless determines the resistance to burning when a sample isignited as the result of an electrical source generated from a highvoltage arc. Tracking, per se, manifests itself at the surface of aninsulation and will readily occur between areas of different electricalpotential any time a semiconducting or conducting film coats the surfaceof an insulation. To accommodate insulations with excellent trackingresistance, modified General Electric equipment was used. First, alarger transformer (6 kv.) was employed. Secondly, the original Nichromewire, which serves as the high voltage electrode, was replaced by aNichrome loop in order to eliminate the tendency of the Nichrome wire topuncture the insulation under test. For the low voltage electrode, adilute aqueous solution of ammonium chloride (containing a non-ionicwetting agent) was used to supply the conducting film. The procedureotherwise followed is described in a paper entitled Dip-Track Test by C.F. Wallace and C. A. Bailey, IEEE Electrical Insulation Group, Paper No.31, pp. 66-360.

9 The results of the above tests are set out below: Materials with anoxygen index ranging from to 27 are considered as slow-burning and thosewith an oxygen index of 28.0 or higher are consideredself-extinguishing.

TABLE A Compositions U.L. horizontal ASTM D-470 P P P U.L. vertical ASTMD2633 P P P Track resistance (kv.) 4.8 4.4 5.0 3.8

NOTE: P=Pass-, F=Fail.

Other properties of the above compositions were measured, and these aretabulated below:

TABLE B Composition Brittleness temp. C 52 57 43 Water absorptionTensile. p.s.i Elongation, persent Aged:

7 days at 121 0.:

Tensile, p.s.i 2,800 3, 300 2, 300 Elongation. percent 290 175 200 7davs at 160 C.:

Tensile. p.s.i 2, 900 2, 900 2,400 1, 550 Elongation, percent 270 1.40160 325 I MgJsq. in. after 7 days at 82 C.

From the above results, it can be seen that deletion of the silane hasan adverse effect on the overall balance of properties.

In another series of runs compositions having the formulations set forthin Table C below were prepared by blending all of the componentstogether in a Banbury mixer. Again care was taken to control thetemperature rise during the mixing to avoid activation of the peroxideprior to completion of blending. The resulting polymeric compositionswere pressed into standard ASTM slabs using a curing press. Propertiesof the slabs where there was no peroxide activation, i.e., nocrosslinking, were then determined using the tests described above. Thisdemonstrates what the properties are when the compositions aremaintained as thermoplastic material, i.e., the

ethylene-vinyl acetate copolymer is non-crosslinked. The

TABLE C P-lO F TAB LE D Elon- LTB Tensile gation,

Composition C (p.s.i.) percent LO I TABLE E Elon- Elon- LTB, Tensilegation, Tensile get-ion, Composition C. (p.s.i.) percent LOI (p.s.i.)percent The above data show that the superior balance of properties aspreviously described, can only be obtained by utilizing a combination ofethylene-vinyl acetate copolymers, silane, and a hydrated organicfiller.

While particular embodiments of this invention are shown above, it willbe understood that the invention is obviously subject to variations andmodifications without departing from its broader aspects. For example,noncrosslinked or crossllnked compositions of the invention may beutilized for many commercial applications as well as in many processingtechniques where flame retardancy is important.

What is claimed is:

1. A flame retardant composition comprising a crosslinkable polymericcomponent containing at least 66% by weight of an ethylene-vinyl acetatecopolyrner, a vinyl alkoxy silane, and from 80 to 400 parts of hydratedaluminum oxide containing chemically bound water per 100 parts of thepolymeric component said vinyl alkoxy silane being present in an amountof from 0.5 to 5 parts per 100 parts of hydrated aluminum oxide.

2. The composition of claim 1 wherein said polymeric component iscrosslinked.

3. The composition of claim 1 wherein said ethylenevinyl acetatecopolymer contains from about 9 to 28% by weight of vinyl acetate.

Composition Amino silane d Calcium steara Antioxidant 2 2 2 2 2 2 2 2Peroxide W 4. 25 4. 25 4. 25 4. 25 42. 5 4. 25 4. 25 4. 25 4. 25

Total 108. 25 233. 25 111. 25 236. 25 236. 25 236. 25 236. 25 236. 25436. 25 235. 25

I 17% vinyl acetate, Melt index 1.3, I h Low density. Melt index 4;

silane: Gemma-amlno-propyltriethoxy-silane; (tert. Butylperoxy-isopropyl) benzene.

Vinyl-tris (beta-methoxyethoxy) Polymerized trimethyldihydro quinoline;

4. A flame retardant composition comprising a crosslinkable polymericcomponent containing at least 66% by weight of an ethylene-vinyl acetatecopolymer, said copolymer having a vinyl acetate content of from about 9to 29% by weight, a lower alkenyl alkoxy silane, and from 80 to 400parts of hydrated aluminum oxide containing chemically bound water per100 parts of the polymeric component, said lower alkenyl alkoxy silanebeing present in an amount of from 0.5 to 5 parts per 100 parts ofhydrated aluminum oxide.

5. The composition of claim 4 wherein said lower alkenyl alkoxy silaneis vinyl tris(beta methoxyethoxy) silane.

References Cited UNITED STATES PATENTS 3,156,666 11/1964 Pruett 260-4l A3,226,356 12/1965 Kehr 260-41 R 12 2,928,802 3/1960 Rehner 26041 A3,290,165 12/1966 Iannicelli 260-41 R 3,563,939 2/1971 Stevens 26041 BOTHER REFERENCES S. Sterman and J. G. Marsden: The Effect of SilaneCoupling Agents in Improving the Properties of Filled or ReinforcedThermoplastics, Technical Papers, Vol. 11, SPE 21st Annual TechnicalConference, March 1965, pp. 1, 3, 4, 10, 13, 14, 17.

P. R. MICHL, Assistant Examiner ALLAN LIEBERMAN, Primary Examiner US.Cl. X.R. 117232; 26042.44, 42.15

